COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2324

                                    Konkoly Observatory
                                    Budapest
                                    29 April 1983

                                    HU ISSN 0374 - 0676



 DIFFERENTIAL UBV-PHOTOMETRY OF THE CHEMICALLY PECULIAR STAR HD 135297


  Babcock (1958) concluded from his 3 Zeeman plates of HD 135297 that this
should have a reversing magnetic field. According to the concept of the 
oblique rotator this is indicative for photometric variability and therefore,
I observed this star in UBV relative to the F2-type comparison star HD 135405
at the 60 cm Bochum telescope on La Silla on 12 nights from May 6 to June 16,
1970. The differential magnitudes (based usually on 3 deflections with a 
typical internal standard deviation of 0.003 mag) are given in the Table.

                    Table
               Log of observations
---------------------------------------
JD             DeltaU  DeltaB  DeltaV
(2440000+)
---------------------------------------
713.80      -0.885   -0.867   -0.431
714.58         896      870      429
714.75         885      869      434
714.83         889      874      426
715.60         875      865      424
715.72         869      873      424
721.73         886      869      432
725.67         876      878      434
727.70         889      878      437
730.71         873      875      427
745.67         899      886      435
749.65         867      878      426
750.62         896      886      439
752.65         873      880      429
754.62      -0.872   -0.877   -0.426
---------------------------------------

Thus the DeltaU-values scatter around the mean DeltaU = -0.882 with a standard 
deviation sigma = 0.0105, the DeltaB-values around DeltaB = -0.875 with sigma = 0.0063 and the DeltaV-
values around DeltaV = -0.430 with sigma = 0.0048.

  It should be noted that the differential magnitudes are given in the 
observer's system.

  Looking at this data one obtains a weak indication that the DeltaU-values
show a periodicity of about 3 days or related to it, but a really meaningful
period search is precluded at the moment by the uneven coverage of the 
observing period and by the overall paucity of data in connection with the low
amplitude indicated by the standard deviations.
  A further check was made using absolute Stromgren-photometry carried out
from March 25 to April 2, 1974, the results of which have been published by
Maitzen (1976). This photometry contained nearly exclusively Ap-stars, and
thus we can only hope to find indications of variability by forming 
differences between HD 135297 and at least two other Ap-stars which were always 
observed closely before or after it. This way I found HD 151525 and HD 137949
as so-called "comparison stars".

  Only the v-filter measurements were regarded since they should exhibit
the largest variation, if any.
Even under these relatively unusual circumstances I obtained:

sigma (Deltav, HD 151525) = 0.0085 (7 measurements)

and

sigma (Deltav, HD 137949) = 0.0068 (5 measurements).

This is in surprising agreement with the sigma of the differential UBV-
measurements. Therefore, one can draw the conclusion that the variability of
HD 135297 is only marginal.




  H.M. MAITZEN
Institut fur Astronomie
der Universitat Wien
  Turkenschanzstr. 17
A - 1180 WIEN, Austria




References:

Babcock, H.W.: 1958, Astrophys. J. Suppl., 3, No. 30. [BIBCODE 1958ApJS....3..141B ]
Maitzen, H.M.: 1976, Astron. Astrophys., 51, 223. [BIBCODE 1976A&A....51..223M ]